Histoplasma skin test

Definition

The histoplasma skin test is used to check if you have been exposed to a fungus called Histoplasma capsulatum. The fungus causes an infection called histoplasmosis.

Alternative Names

Histoplasmosis skin test

How the Test is Performed

Your health care provider cleans an area of your skin, usually the forearm. An allergen is injected just below the cleaned skin surface. An allergen is a substance that causes an allergic reaction. The injection site is checked at 24 hours and at 48 hours for signs of a reaction. Occasionally, the reaction may not appear until the fourth day.

How to Prepare for the Test

No special preparation is necessary for this test.

How the Test will Feel

You may feel a brief sting as the needle is inserted just below the skin.

Why the Test is Performed

This test is used to determine if you have been exposed to the fungus that causes histoplasmosis.

Normal Results

No reaction (inflammation) at the site of the test is normal. The skin test can rarely make histoplasmosis antibody tests turn positive.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

A reaction means you have been exposed to Histoplasma capsulatum. It does not mean you have an active infection.

Risks

There is a slight risk of anaphylactic shock (a severe reaction).

Considerations

This test is rarely used today. It has been replaced by a variety of blood and urine tests.

References

Deepe GS. Histoplasma capsulatum (histoplasmosis). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 263.

Iwen PC, Thompson GR, Wiederhold NP. Mycotic diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 60.